| Abstract |
The common cutworm, Spodoptera litura, is a serious insect pest of many vegetables and crops worldwide. Entomopathogenic nematodes (EPN) have been utilized as biological control agents for controlling various insect pests, including the larvae of S. litura. Many indigenous EPN have been recognized to be more effective in specific field applications. Among the 160 soil samples collected in undisturbed areas of western Thailand, three samples tested positive for EPN. Three indigenous EPN were identified as Steinernema siamkayai namely, EPNKU63, EPNKU70 and EPNKU85, based on ITS and D2/D3 expansion region analysis of the 28s rRNA genes. Additionally, genetic analysis of the symbiotic bacteria using recA rRNA sequences confirmed their identity as Xenorhabdus stockiae namely, PEPNKU63, PEPNKU70 and PEPNKU85. To evaluate their initial biocontrol potential against the 6th instar larvae of Galleria mellonella, virulence assays were conducted. The application of 100 infective juveniles (IJs)/insects resulted in the mortality of 80鈥�100% of G. mellonella larvae after 72鈥塰. When symbiotic bacteria were applied at 1鈥壝椻��106 cells/insect, they exhibited 63鈥�93% mortality against G. mellonella larvae after 120鈥塰. In further laboratory tests, three S. siamkayai isolates achieved 100% mortality of 3rd instar Spodoptera litura larvae within 72鈥塰, with LC50 values ranging from 29 to 30 IJs/insect. In screenhouse experiments, it was revealed that all S. siamkayai isolates displayed substantial virulence, ranging from 62% to 74%, against 3rd instar S. litura larvae within 72鈥塰. This study demonstrates the biocontrol potential of S. siamkayai in controlling S. litura larvae. |
Mindanao State
University - Iligan Institute of Technology